body {
  font-family: Avenir, Helvetica, Arial, sans-serif;
  margin: 0;
  padding: 0;
  background-color: #f4f4f4;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 20px;
}

@media (max-width: 768px) {
  .navbar ul {
    flex-direction: column;
  }

  .navbar li {
    text-align: center;
    margin: 10px 0;
  }
}